revolution of dna sequencing method from the past until today

dna sequence determination is a tremendous human achievement. dna sequencing includes several methods and technologies in use for determining the order of the nucleotide bases (adenine, guanine, cytosine, and thymine) in a molecule of dna. knowledge of dna sequences has become indispensable for basic biological research, other research branches utilizing dna sequencing, and in numerous applied fields such as diagnostic, biotechnology, forensic biology and biological systematics. the advent of dna sequencing has significantly accelerated biological research and discovery. rapid sequencing, the result of modern dna sequencing technology, is instrumental in the sequencing of the human genome for the human genome project. related projects, often by scientific collaboration across continents, have generated complete dna sequences of humans as well as numerous animals, plants and microbial genomes. dna sequencing methods currently under development include labeling dna polymerase and reading the sequence as a dna strand transits through nanopores. additional methods include microscopy-based techniques such as atomic force microscopy or transmission electron microscopy that are used to identify the positions of individual nucleotides within long dna fragments (>5000 bp) by nucleotide labeling with heavier elements (e.g., halogens) for visual detection and recording. third generation technologies aim to increase throughput and decrease the time to result and cost by eliminating the need for excessive reagents and harnessing the processivity of dna polymerase. researchers in the field of genetics in iran use this technology in their studies, but unfortunately our literature lack proper persian language resources. the authors intend to write a series of review articles in this field. the present paper is an introduction to the summary of important techniques in dna sequencing.